The Mammoth Lakes area is experiencing a series of micro-quakes, just south of Mammoth Mountain. You can see the small blue squares in this image, near the bottom. That means that the swarm happened within the last 24 hours. The somewhat larger yellow squares to the northeast of the swarm is the continuation of a months long earthquake swarm near Hawthorne, Nevada.
In my opinion, there is volcanic plumbing or a high temperature water system that connects these two areas. This is just my thought and not at all a fact. Something like that would have to be researched and tested before it is a fact. That requires a lot of expensive surveys, including those from space and the air. NASA would have to play a part in the surveys, as they did right after the big 7.2 magnitude earthquake near Mexicali over a year ago.
Something is indeed brewing near Hawthorne, Nevada, and this is a very long lasting earthquake swarm. The little swarm near Mammoth is fresh, and is normally an off and on activity - as magma cools and cracks, or as high pressure hot water moves through fissures and natural plumbing.
Here's the USGS link. The image above is from the USGS.